laboratoire de physique statistique
 
 
laboratoire de physique statistique

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FLUID DYNAMICS RESEARCH 


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2015
Laminar-turbulent patterning in wall-bounded shear flows: a Galerkin model - Seshasayanan, K. and Manneville, P.
FLUID DYNAMICS RESEARCH 47 (2015)

Abstract : On its way to turbulence, plane Couette flow-the flow between counter-translating parallel plates-displays a puzzling steady oblique laminar-turbulent pattern. We approach this problem via Galerkin modelling of the Navier-Stokes equations. The wall-normal dependence of the hydrodynamic field is treated by means of expansions on functional bases fitting the boundary conditions exactly. This yields a set of partial differential equations for spatiotemporal dynamics in the plane of the flow. Truncating this set beyond the lowest nontrivial order is numerically shown to produce the expected pattern, therefore improving over what was obtained at the cruder effective wall-normal resolution. Perspectives opened by this approach are discussed.
 
2009
Capturing reconnection phenomena using generalized Eulerian-Lagrangian description in Navier-Stokes and resistive MHD - Cartes, Carlos and Bustamante, Miguel D. and Pouquet, Annick and Brachet, Marc E.
FLUID DYNAMICS RESEARCH 41 (2009)

Abstract : New generalized equations of motion for the Weber-Clebsch potentials that describe both the Navier-Stokes and magnetohydrodynamics (MHD) dynamics are derived. These depend on a new parameter, which has dimensions of time for Navier-Stokes and inverse velocity for MHD. Direct numerical simulations (DNSs) are performed. For Navier-Stokes, the generalized formalism captures the intense reconnection of vortices of the Boratav, Pelz and Zabusky (BPZ) flow, in agreement with the previous study by Ohkitani and Constantin. For MHD, the new formalism is used to detect magnetic reconnection in several flows: the three-dimensional (3D) Arnold, Beltrami and Childress (ABC) flow and the (2D and 3D) Orszag-Tang (OT) vortex. It is concluded that periods of intense activity in the magnetic enstrophy are correlated with periods of increasingly frequent resettings. Finally, the positive correlation between the sharpness of the increase in resetting frequency and the spatial localization of the reconnection region is discussed.